1. Field of the Invention
This invention relates to a mining machine, and more particularly to a scrubber system for dust control on a mining machine in which a duct assembly is provided with fan assemblies mounted upstream of a scrubber, a demister positioned downstream of the scrubber, and a rear crossover discharge duct.
2. Description of the Prior Art
In underground mining, mining machines having a material dislodging means positioned on the front end of the mining machine for dislodging material from a mine face are well known. The dislodged material is conveyed by a conveying system extending rearwardly on the mining machine. The mining machine advances into the mine face to dislodge material to form an entry or tunnel in the material seam. It is also well known in underground mining to provide a mining machine with a dust collection system, and various types of mining machines having different types of duct assemblies are known.
U.S. Pat. No. 2,375,689 discloses an apparatus for the removal of coal from a vein by grinding the vein of coal into a powder and removing the powdered coal by suction. A rotary grinding wheel is positioned against the vein of coal and the resultant powdered coal is withdrawn by means of a suction source.
U.S Pat. No. 4,076,315 discloses a dust collecting system for use in conjunction with a continuous mining machine which includes a duct assembly having an opening adjacent the material dislodging means of the continuous mining machine. The duct assembly has within it a fan assembly, the blades of which are wetted while inducing a flow of air through an opening in the duct assembly adjacent the mining machine material dislodging means. The fan blades also act as a scrubber by means of the impingement of the particles of dust in the air upon the wetted fan blades. The resultant cleaned air and coal slurry is redirected to the mining machine material dislodging means to further reduce dust concentration.
U.S. Pat. No. 4,193,778 discloses a gas scrubber with a plurality of venturi tubes having upstream ends communicating with the air inlet and being arranged parallel to each other. A centrifugal separator is in communication with the downstream ends of the venturi tubes. A blower means for drawing dust laden air into the upstream ends of the venturi tubes and from there into a centrifugal separator is also disclosed. Water is introduced into the venturi tubes in a mist by means of a nozzle. A funnel which widens in the air flow direction and which has a porous air filter across the outlet end of the funnel discharges the cleaned air.
U.S. Pat. No. 4,289,509 discloses a dust collecting system which includes a fan assembly for withdrawing air from the mine face and into a ductwork assembly. Upstream from the fan is an agglomerating chamber wherein the dust-entrained air is wetted. The dust particles are suspended in water droplets in the air. As the water droplets impringe upon a series of vanes they are separated from the air.
U.S. Pat. No. 4,380,353 discloses a dust collecting system comprising a ductwork assembly extending along one side of a continuous mining machine and having an opening adjacent the material dislodging means of the mining machine. A vane axial fan is located in the duct assembly at the rear end of the mining machine, and a scrubber is located upstream of the fan assembly. Between the scrubber and the fan assembly is a demister with an associated sump.
U.S. Pat. No. 4,388,087 discloses a filter for the separation of particulate matter from a flowing gas stream. A cyclone type separator-filter unit is provided with a centrifugal blower integrally mounted to the unit to induce a vacuum within the entire unit. Pleated paper filter elements are utilized as secondary barrier filters.
U.S. Pat. No. 4,869,737 discloses a vehicle for use in conjunction with a conventional coal mining machine. The vehicle has a frame and wheels and is designed to work closely with the coal mining machine to clean dust entrained air produced by the material dislodging means of the mining machine. The vehicle has an air inlet connected to a plurality of individual centrifugal filters which open into a separator core element. The air then passes into a plurality of individual filters by means of a main suction blower.
Although the prior art discloses gas filtering systems and mining machines having dust collecting systems, there remains a need for a mining machine having a dust collection system with a fan assembly mounted upstream of the scrubber and demister of the dust collection system to efficiently utilize the space otherwise occupied by the fan assembly at the rear of the mining machine frame. Further, there is need to reduce the overall length of the mining machine as presently encountered with a rear crossover portion of a duct assembly extending behind the bumper at the rearward end of the mining machine.